Inbred maize line PH20A

ABSTRACT

An inbred maize line, designated PH20A, the plants and seeds of inbred maize line PH20A, methods for producing a maize plant produced by crossing the inbred line PH20A with itself or with another maize plant, and hybrid maize seeds and plants produced by crossing the inbred line PH20A with another maize line or plant.

FIELD OF THE INVENTION

This invention is in the field of maize breeding, specifically relatingto an inbred maize line designated PH20A.

BACKGROUND OF THE INVENTION

The goal of plant breeding is to combine in a single variety or hybridvarious desirable traits. For field crops, these traits may includeresistance to diseases and insects, tolerance to heat and drought,reducing the time to crop maturity, greater yield, and better agronomicquality. With mechanical harvesting of many crops, uniformity of plantcharacteristics such as germination and stand establishment, growthrate, maturity, and plant and ear height, is important.

Field crops are bred through techniques that take advantage of theplants method of pollination. A plant is self-pollinated if pollen fromone flower is transferred to the same or another flower of the sameplant. A plant is cross-pollinated if the pollen comes from a flower ona different plant.

Plants that have been self-pollinated and selected for type for manygenerations become homozygous at almost all gene loci and produce auniform population of true breeding progeny. A cross between twodifferent homozygous lines produces a uniform population of hybridplants that may be heterozygous for many gene loci. A cross of twoplants each heterozygous at a number of gene loci will produce apopulation of hybrid plants that differ genetically and will not beuniform.

Maize (zea mays L.), often referred to as corn in the United States, canbe bred by both self-pollination and cross-pollination techniques. Maizehas separate male and female flowers on the same plant, located on thetassel and the ear, respectively. Natural pollination occurs in maizewhen wind blows pollen from the tassels to the silks that protrude fromthe tops of the ears.

A reliable method of controlling male fertility in plants offers theopportunity for improved plant breeding. This is especially true fordevelopment of maize hybrids, which relies upon some sort of malesterility system. There are several options for controlling malefertility available to breeders, such as: manual or mechanicalemasculation (or detasseling), cytoplasmic male sterility, genetic malesterility, gametocides and the like.

Hybrid maize seed is typically produced by a male sterility systemincorporating manual or mechanical detasseling. Alternate strips of twoinbred varieties of maize are planted in a field, and the pollen-bearingtassels are removed from one of the inbreds (female). Providing thatthere is sufficient isolation from sources of foreign maize pollen, theears of the detasseled inbred will be fertilized only from the otherinbred (male), and the resulting seed is therefore hybrid and will formhybrid plants.

The laborious, and occasionally unreliable, detasseling process can beavoided by using cytoplasmic male-sterile (CMS) inbreds. Plants of a CMSinbred are male sterile as a result of factors resulting from thecytoplasmic, as opposed to the nuclear, genome. Thus, thischaracteristic is inherited exclusively through the female parent inmaize plants, since only the female provides cytoplasm to the fertilizedseed. CMS plants are fertilized with pollen from another inbred that isnot male-sterile. Pollen from the second inbred may or may notcontribute genes that make the hybrid plants male-fertile. Usually seedfrom detasseled fertile maize and CMS produced seed of the same hybridare blended to insure that adequate pollen loads are available forfertilization when the hybrid plants are grown.

There are several methods of conferring genetic male sterilityavailable, such as multiple mutant genes at separate locations withinthe genome that confer male sterility, as disclosed in U.S. Pat. Nos.4,654,465 and 4,727,219 to Brar et al. and chromosomal translocations asdescribed by Patterson in U.S. Pat. Nos. 3,861,709 and 3,710,511. Theseand all patents referred to are incorporated by reference. In additionto these methods, Albertsen et al., of Pioneer Hi-Bred, U.S. patentapplication Ser. No. 07/848,433, have developed a system of nuclear malesterility which includes: identifying a gene which is critical to malefertility; silencing this native gene which is critical to malefertility; removing the native promoter from the essential malefertility gene and replacing it with an inducible promoter; insertingthis genetically engineered gene back into the plant; and thus creatinga plant that is male sterile because the inducible promoter is not "on"resulting in the male fertility gene not being transcribed. Fertility isrestored by inducing, or turning "on", the promoter, which in turnallows the gene that confers male fertility to be transcribed.

There are many other methods of conferring genetic male sterility in theart, each with its own benefits and drawbacks. These methods use avariety of approaches such as delivering into the plant a gene encodinga cytotoxic substance associated with a male tissue specific promoter oran antisense system in which a gene critical to fertility is identifiedand an antisense to that gene is inserted in the plant (see:Fabinjanski, et al. EPO 89/3010153.8 publication no. 329,308 and PCTapplication PCT/CA90100037 published as WO 90/08828).

Another system useful in controlling male sterility makes use ofgametocides. Gametocides are not a genetic system, but rather a topicalapplication of chemicals. These chemicals affect cells that are criticalto male fertility. The application of these chemicals affects fertilityin the plants only for the growing season in which the gametocide isapplied (see Carison, Glenn R., U.S. Pat. No.: 4,936,904). Applicationof the gametocide, timing of the application and genotype specificityoften limit the usefulness of the approach.

The use of male sterile inbreds is but one factor in the production ofmaize hybrids. The development of maize hybrids requires, in general,the development of homozygous inbred lines, the crossing of these lines,and the evaluation of the crosses. Pedigree breeding and recurrentselection breeding methods are used to develop inbred lines frombreeding populations. Breeding programs combine the genetic backgroundsfrom two or more inbred lines or various other broad-based sources intobreeding pools from which new inbred lines are developed by selfing andselection of desired phenotypes. The new inbreds are crossed with otherinbred lines and the hybrids from these crosses are evaluated todetermine which of those have commercial potential.

Pedigree breeding starts with the crossing of two genotypes, each ofwhich may have one or more desirable characteristics that is lacking inthe other or which complements the other. If the two original parents donot provide all the desired characteristics, other sources can beincluded in the breeding population. In the pedigree method, superiorplants are selfed and selected in successive generations. In thesucceeding generations the heterozygous condition gives way tohomogeneous lines as a result of self-pollination and selection.Typically in the pedigree method of breeding five or more generations ofselfing and selection is practiced: F₁ →F₂ ; F₃ →F₄ ; F₄ →F₅, etc.

Recurrent selection breeding, backcrossing for example, can be used toimprove an inbred line. Backcrossing can be used to transfer a specificdesirable trait from one inbred or source to an inbred that lacks thattrait. This can be accomplished, for example, by first crossing asuperior inbred (recurrent parent) to a donor inbred (non-recurrentparent), that carries the appropriate gene(s) for the trait in question.The progeny of this cross is then mated back to the superior recurrentparent followed by selection in the resultant progeny for the desiredtrait to be transferred from the non-recurrent parent. After five ormore backcross generations with selection for the desired trait, theprogeny will be heterozygous for loci controlling the characteristicbeing transferred, but will be like the superior parent for most oralmost all other genes. The last backcross generation is then selfed togive pure breeding progeny for the gene(s) being transferred.

A single cross hybrid maize variety is the cross of two inbred lines,each of which has a genotype that complements the genotype of the other.The hybrid progeny of the first generation is designated F₁. In thedevelopment of hybrids only the F₁ hybrid plants are sought. PreferredF₁ hybrids are more vigorous than their inbred parents. This hybridvigor, or heterosis, can be manifested in many polygenic traits,including increased vegetative growth and increased yield.

The development of a hybrid maize variety involves three steps: (1) theselection of plants from various germplasm pools for initial breedingcrosses; (2) the selfing of the selected plants from the breedingcrosses for several generations to produce a series of inbred lines,which, although different from each other, breed true and are highlyuniform; and (3) crossing the selected inbred lines with differentinbred lines to produce the hybrid progeny (F₁). During the inbreedingprocess in maize, the vigor of the lines decreases. Vigor is restoredwhen two different inbred lines are crossed to produce the hybridprogeny (F₁). An important consequence of the homozygosity andhomogeneity of the inbred lines is that the hybrid between a definedpair of inbreds will always be the same. Once the inbreds that give asuperior hybrid have been identified, the hybrid seed can be reproducedindefinitely as long as the homogeneity of the inbred parents ismaintained.

A single cross hybrid is produced when two inbred lines are crossed toproduce the F₁ progeny. A double cross hybrid is produced from fourinbred lines crossed in pairs (A×B and C×D) and then the two F₁ hybridsare crossed again (A×B)×(C×D). Much of the hybrid vigor exhibited by F₁hybrids is lost in the next generation (F₂). Consequently, seed fromhybrid varieties is not used for planting stock.

Maize is an important and valuable field crop. Thus, a continuing goalof plant breeders is to develop high-yielding maize hybrids that areagronomically sound based on stable inbred lines. The reasons for thisgoal are obvious: to maximize the amount of grain produced with theinputs used and minimize susceptibility of the crop to environmentalstresses. To accomplish this goal, the maize breeder must select anddevelop superior inbred parental lines for producing hybrids. Thisrequires identification and selection of genetically unique individualsthat occur in a segregating population. The segregating population isthe result of a combination of crossover events plus the independentassortment of specific combinations of alleles at many gene loci thatresults in specific genotypes. Based on the number of segregating genes,the frequency of occurrence of an individual with a specific genotype isless than 1 in 10,000. Thus, even if the entire genotype of the parentshas been characterized and the desired genotype is known, only a few ifany individuals having the desired genotype may be found in a large F₂or S₀ population. Typically, however, the genotype of neither theparents nor the desired genotype is known in any detail.

In addition to the preceding problem, it is not known how the genotypewill react with the environment. This genotype by environmentinteraction is an important, yet unpredictable, factor in plantbreeding. A breeder of ordinary skill in the art cannot predict thegenotype, how that genotype will interact with various environments orthe resulting phenotypes of the developing lines, except perhaps in avery broad and general fashion. A breeder of ordinary skill in the artwould also be unable to recreate the same line twice from the very sameoriginal parents as the breeder is unable to direct how the genomescombine or how they will interact with the environmental conditions.This unpredictability results in the expenditure of large amounts ofresearch resources in the development of a superior new maize inbredline.

Pioneer research station staff propose about 400 to 500 new inbreds eachyear from over 2,000,000 pollinations. Of those proposed new inbreds,less than 50 and more commonly less than 30 are actually selected forcommercial use.

SUMMARY OF THE INVENTION

According to the invention, there is provided a novel inbred maize line,designated PH20A. This invention thus relates to the seeds of inbredmaize line PH20A, to the plants of inbred maize line PH20A, and tomethods for producing a maize plant produced by crossing the inbred linePH20A with itself or another maize line. This invention further relatesto hybrid maize seeds and plants produced by crossing the inbred linePH20A with another maize line.

DEFINITIONS

In the description and examples that follow, a number of terms are usedherein. in order to provide a clear and consistent understanding of thespecification and claims, including the scope to be given such terms,the following definitions are provided. NOTE: ABS is in absolute termsand % MN is percent of the mean for the experiments in which the inbredor hybrid was grown. These designators will follow the descriptors todenote how the values are to be interpreted. Below are the descriptorsused in the data tables included herein.

ANT ROT=ANTHRACNOSE STALK ROT (Colletotrichum graminicola). A 1 to 9visual rating indicating the resistance to Anthracnose Stalk Rot. Ahigher score indicates a higher resistance.

BAR PLT=BARREN PLANTS. The percent of plants per plot that were notbarren (lack ears).

BRT STK=BRITTLE STALKS. This is a measure of the stalk breakage near thetime of pollination, and is an indication of whether a hybrid or inbredwould snap or break near the time of flowering under severe winds. Dataare presented as percentage of plants that did not snap.

BU ACR=YIELD (BUSHELS/ACRE). Yield of the grain at harvest in bushelsper acre adjusted to 15.5% moisture.

CLD TST=COLD TEST. The percent of plants that germinate under cold testconditions.

CLN=CORN LETHAL NECROSIS. Synergistic interaction of maize chloroticmottle virus (MCMV) in combination with either maize dwarf mosaic virus(MDMV-A or MDMV-B) or wheat streak mosaic virus (WSMV). A 1 to 9 visualrating indicating the resistance to Corn Lethal Necrosis. A higher scoreindicates a higher resistance.

COM RST=COMMON RUST (Puccinia sorghi). A 1 to 9 visual rating indicatingthe resistance to Common Rust. A higher score indicates a higherresistance.

D/D=DRYDOWN. This represents the relative rate at which a hybrid willreach acceptable harvest moisture compared to other hybrids on a 1-9rating scale. A high score indicates a hybrid that dries relatively fastwhile a low score indicates a hybrid that dries slowly.

DIP ERS=DIPLODIA EAR MOLD SCORES (Diplodia maydis and Diplodiamacrospora). A 1 to 9 visual rating indicating the resistance toDiplodia Ear Mold. A higher score indicates a higher resistance.

DRP EAR=DROPPED EARS. A measure of the number of dropped ears per plotand represents the percentage of plants that did not drop ears prior toharvest.

D/T=DROUGHT TOLERANCE. This represents a 1-9 rating for droughttolerance, and is based on data obtained under stress conditions. A highscore indicates good drought tolerance and a low score indicates poordrought tolerance.

EAR HT=EAR HEIGHT. The ear height is a measure from the ground to thehighest placed developed ear node attachment and is measured in inches.

EAR MLD=General Ear Mold. Visual rating (1-9 score) where a "1" is verysusceptible and a "9" is very resistant. This is based on overall ratingfor ear mold of mature ears without determining the specific moldorganism, and may not be predictive for a specific ear mold.

EAR SZ=EAR SIZE. A 1 to 9 visual rating of ear size. The higher therating the larger the ear size.

ECB 1LF=EUROPEAN CORN BORER FIRST GENERATION LEAF FEEDING (Ostrinianubilalis). A 1 to 9 visual rating indicating the resistance topreflowering leaf feeding by first generation European Corn Borer. Ahigher score indicates a higher resistance.

ECB 21T=EUROPEAN CORN BORER SECOND GENERATION INCHES OF TUNNELING(Ostrnia nubilalis). Average inches of tunneling per plant in the stalk.

ECB 2SC=EUROPEAN CORN BORER SECOND GENERATION (Ostrinia nubilalis). A 1to 9 visual rating indicating post flowering degree of stalk breakageand other evidence of feeding by European Corn Borer, Second Generation.A higher score indicates a higher resistance.

ECB DPE=EUROPEAN CORN BORER DROPPED EARS (Ostrinia nubilalis). Droppedears due to European Corn Borer. Percentage of plants that did not dropears under second generation corn borer infestation.

EST CNT=EARLY STAND COUNT. This is a measure of the stand establishmentin the spring and represents the number of plants that emerge on perplot basis for the inbred or hybrid.

EYE SPT=Eye Spot (Kabatiella zeae or Aureobasidium zeae). A 1 to 9visual rating indicating the resistance to Eye Spot. A higher scoreindicates a higher resistance.

FUS ERS=FUSARIUM EAR ROT SCORE (Fusarium monilifonne or Fusariumsubglutinans). A 1 to 9 visual rating indicating the resistance toFusarium ear rot. A higher score indicates a higher resistance.

GDU=Growing Degree Units. Using the Barger Heat Unit Theory, whichassumes that maize growth occurs in the temperature range 50° F.-86° F.and that temperatures outside this range slow down growth; the maximumdaily heat unit accumulation is 36 and the minimum daily heat unitaccumulation is 0. The seasonal accumulation of GDU is a major factor indetermining maturity zones.

GDU SHD=GDU TO SHED. The number of growing degree units (GDUs) or heatunits required for an inbred line or hybrid to have approximately 50percent of the plants shedding pollen and is measured from the time ofplanting. Growing degree units are calculated by the Barger Method,where the heat units for a 24-hour period are: ##EQU1##

The highest maximum temperature used is 86° F. and the lowest minimumtemperature used is 50° F. For each inbred or hybrid it takes a certainnumber of GDUs to reach various stages of plant development.

GDU SLK=GDU TO SILK. The number of growing degree units required for aninbred line or hybrid to have approximately 50 percent of the plantswith silk emergence from time of planting. Growing degree units arecalculated by the Barger Method as given in GDU SHD definition.

GIB ERS=GIBBERELLA EAR ROT (PINK MOLD) (Gibberella zeae). A 1 to 9visual rating indicating the resistance to Gibberella Ear Rot. A higherscore indicates a higher resistance.

GLF SPT=Gray Leaf Spot (Cercospora zeae-maydis). A 1 to 9 visual ratingindicating the resistance to Gray Leaf Spot. A higher score indicates ahigher resistance.

GOS WLT=Goss' Wilt (Corynebacterium nebraskense). A 1 to 9 visual ratingindicating the resistance to Goss' Wilt. A higher score indicates ahigher resistance.

GRN APP=GRAIN APPEARANCE. This is a 1 to 9 rating for the generalappearance of the shelled grain as it is harvested based on such factorsas the color of harvested grain, any mold on the grain, and any crackedgrain. High scores indicate good grain quality.

H/POP=YIELD AT HIGH DENSITY. Yield ability at relatively high plantdensities on 1-9 relative rating system with a higher number indicatingthe hybrid responds well to high plant densities for yield relative toother hybrids. A 1, 5, and 9 would represent very poor, average, andvery good yield response, respectively, to increased plant density.

HC BLT=HELMINTHOSPORIUM CARBONUM LEAF BLIGHT (Helminthosporiumcarbonum). A 1 to 9 visual rating indicating the resistance toHelminthosporium infection. A higher score indicates a higherresistance.

HD SMT=HEAD SMUT (Sphacelotheca reiliana). This score indicates thepercentage of plants not infected.

INC D/A=GROSS INCOME (DOLLARS PER ACRE). Relative income per acreassuming drying costs of two cents per point above 15.5 percent harvestmoisture and current market price per bushel.

INCOME/ACRE. Income advantage of hybrid to be patented over other hybridon per acre basis.

INC ADV=GROSS INCOME ADVANTAGE. GROSS INCOME advantage of variety #1over variety #2.

KSZ DCD=KERNEL SIZE DISCARD. The percent of discard seed; calculated asthe sum of discarded tip kernels and extra large kernels.

UPOP=YIELD AT LOW DENSITY. Yield ability at relatively low plantdensities on a 1-9 relative system with a higher number indicating thehybrid responds well to low plant densities for yield relative to otherhybrids. A 1, 5, and 9 would represent very poor, average, and very goodyield response, respectively, to low plant density.

MDM CPX=MAIZE DWARF MOSAIC COMPLEX (MDMV=Maize Dwarf Mosaic Virus andMCDV=Maize Chlorotic Dwarf Virus). A 1 to 9 visual rating indicating theresistance to Maize Dwarf Mosaic Complex. A higher score indicates ahigher resistance.

MST=HARVEST MOISTURE. The moisture is the actual percentage moisture ofthe grain at harvest.

MST ADV=MOISTURE ADVANTAGE. The moisture advantage of variety #1 overvariety #2 as calculated by: MOISTURE of variety #2-MOISTURE of variety#1=MOISTURE ADVANTAGE of variety #1.

NLF BLT=Northern Leaf Blight (Helminthosporium turcicum or Exserohilumturcicum). A 1 to 9 visual rating indicating the resistance to NorthernLeaf Blight. A higher score indicates a higher resistance.

PLT HT=PLANT HEIGHT. This is a measure of the height of the plant fromthe ground to the tip of the tassel in inches.

POL SC=POLLEN SCORE. A 1 to 9 visual rating indicating the amount ofpollen shed. The higher the score the more pollen shed.

POL WT=POLLEN WEIGHT. This is calculated by dry weight of tasselscollected as shedding commences minus dry weight from similar tasselsharvested after shedding is complete.

It should be understood that the inbred can, through routinemanipulation of cytoplasmic or other factors, be produced in amale-sterile form. Such embodiments are also contemplated within thescope of the present claims.

POP K/A=PLANT POPULATIONS. Measured as 1000s per acre.

POP ADV=PLANT POPULATION ADVANTAGE. The plant population advantage ofvariety #1 over variety #2 as calculated by PLANT POPULATION of variety#2-PLANT POPULATION of variety #1=PLANT POPULATION ADVANTAGE of variety#1.

PRM=PREDICTED RELATIVE MATURITY. This trait, predicted relativematurity, is based on the harvest moisture of the grain. The relativematurity rating is based on a known set of checks and utilizes standardlinear regression analyses and is also referred to as the ComparativeRelative Maturity Rating System that is similar to the MinnesotaRelative Maturity Rating System.

PRM SHD=A relative measure of the growing degree units (GDU) required toreach 50% pollen shed. Relative values are predicted values from thelinear regression of observed GDU's on relative maturity of commercialchecks.

RT LDG=ROOT LODGING. Root lodging is the percentage of plants that donot root lodge; plants that lean from the vertical axis at anapproximately 300 angle or greater would be counted as root lodged.

RTL ADV=ROOT LODGING ADVANTAGE. The root lodging advantage of variety #1over variety #2.

SCT GRN=SCATTER GRAIN. A 1 to 9 visual rating indicating the amount ofscatter grain (lack of pollination or kernel abortion) on the ear. Thehigher the score the less scatter grain.

SDG VGR=SEEDLING VIGOR. This is the visual rating (1 to 9) of the amountof vegetative growth after emergence at the seedling stage(approximately five leaves). A higher score indicates better vigor.

SEL IND=SELECTION INDEX. The selection index gives a single measure ofthe hybrid's worth based on information for up to five traits. A maizebreeder may utilize his or her own set of traits for the selectionindex. One of the traits that is almost always included is yield. Theselection index data presented in the tables represent the mean valueaveraged across testing stations.

SLF BLT=SOUTHERN LEAF BLIGHT (Helminthosporium maydis or Bipolarismaydis). A 1 to 9 visual rating indicating the resistance to SouthernLeaf Blight. A higher score indicates a higher resistance.

SOU RST=SOUTHERN RUST (Puccinia polysora). A 1 to 9 visual ratingindicating the resistance to Southern Rust. A higher score indicates ahigher resistance.

STA GRN=STAY GREEN. Stay green is the measure of plant health near thetime of black layer formation (physiological maturity). A high scoreindicates better late-season plant health.

STD ADV=STALK STANDING ADVANTAGE. The advantage of variety #1 overvariety #2 for the trait STK CNT.

STK CNT=NUMBER OF PLANTS. This is the final stand or number of plantsper plot.

STK LDG=STALK LODGING. This is the percentage of plants that did notstalk lodge (stalk breakage) as measured by either natural lodging orpushing the stalks and determining the percentage of plants that breakbelow the ear.

STW WLT=Stewart's Wilt (Erwinia stewartii). A 1 to 9 visual ratingindicating the resistance to Stewart's Wilt. A higher score indicates ahigher resistance.

TAS BLS=TASSEL BLAST. A 1 to 9 visual rating was used to measure thedegree of blasting (necrosis due to heat stress) of the tassel at thetime of flowering. A 1 would indicate a very high level of blasting attime of flowering, while a 9 would have no tassel blasting.

TAS SZ=TASSEL SIZE. A 1 to 9 visual rating was used to indicate therelative size of the tassel. The higher the rating the larger thetassel.

TAS WT=TASSEL WEIGHT. This is the average weight of a tassel (grams)just prior to pollen shed.

TEX EAR=EAR TEXTURE. A 1 to 9 visual rating was used to indicate therelative hardness (smoothness of crown) of mature grain. A 1 would bevery soft (extreme dent) while a 9 would be very hard (flinty or verysmooth crown).

TILLER=TILLERS. A count of the number of tillers per plot that couldpossibly shed pollen was taken. Data is given as a percentage oftillers: number of tillers per plot divided by number of plants perplot.

TST WT=TEST WEIGHT (UNADJUSTED). The measure of the weight of the grainin pounds for a given volume (bushel).

TST WTA=TEST WEIGHT ADJUSTED. The measure of the weight of the grain inpounds for a given volume (bushel) adjusted for 15.5 percent moisture.

TSW ADV=TEST WEIGHT ADVANTAGE. The test weight advantage of variety #1over variety #2.

WIN M %=PERCENT MOISTURE WINS.

WIN Y %=PERCENT YIELD WINS.

YLD=YIELD. It is the same as BU ACR ABS.

YLD ADV=YIELD ADVANTAGE. The yield advantage of variety #1 over variety#2 as calculated by: YIELD of variety #1-YIELD variety #2=yieldadvantage of variety #1.

YLD SC=YIELD SCORE. A 1 to 9 visual rating was used to give a relativerating for yield based on plot ear piles. The higher the rating thegreater visual yield appearance.

DETAILED DESCRIPTION OF THE INVENTION

Inbred maize lines are typically developed for use in the production ofhybrid maize lines. Inbred maize lines need to be highly homogeneous,homozygous and reproducible to be useful as parents of commercialhybrids. There are many analytical methods available to determine thehomozygotic and phenotypic stability of these inbred lines.

The oldest and most traditional method of analysis is the observation ofphenotypic traits. The data is usually collected in field experimentsover the life of the maize plants to be examined. Phenotypiccharacteristics most often observed are for traits associated with plantmorphology, ear and kernel morphology, insect and disease resistance,maturity, and yield.

In addition to phenotypic observations, the genotype of a plant can alsobe examined. There are many laboratory-based techniques available forthe analysis, comparison and characterization of plant genotype; amongthese are Isozyme Electrophoresis, Restriction Fragment LengthPolymorphisms (RFLPs), Randomly Amplified Polymorphic DNAs (RAPDs),Arbitrarily Primed Polymerase Chain Reaction (AP-PCR), DNA AmplificationFingerprinting (DAF), Sequence Characterized Amplified Regions (SCARs),Amplified Fragment Length Polymorphisms (AFLPs), and Simple SequenceRepeats (SSRs) which are also referred to as Microsatellites.

The most widely used of these laboratory techniques are IsozymeElectrophoresis and RFLPs as discussed in Lee, M., "Inbred Lines ofMaize and Their Molecular Markers," The Maize Handbook,(Springer-Verlag, New York, Inc. 1994, at 423-432) incorporated hereinby reference. Isozyme Electrophoresis is a useful tool in determininggenetic composition, although it has relatively low number of availablemarkers and the low number of allelic variants among maize inbreds.RFLPs have the advantage of revealing an exceptionally high degree ofallelic variation in maize and the number of available markers is almostlimitless.

Maize RFLP linkage maps have been rapidly constructed and widelyimplemented in genetic studies. One such study is described inBoppenmaier, et al., "Comparisons among strains of inbreds for RFLPS",Maize Genetics Cooperative Newsletter, 65:1991, pg. 90, is incorporatedherein by reference. This study used 101 RFLP markers to analyze thepatterns of 2 to 3 different deposits each of five different inbredlines. The inbred lines had been selfed from 9 to 12 times before beingadopted into 2 to 3 different breeding programs. It was results fromthese 2 to 3 different breeding programs that supplied the differentdeposits for analysis. These five lines were maintained in the separatebreeding programs by selfing or sibbing and rogueing off-type plants foran additional one to eight generations. After the RFLP analysis wascompleted, it was determined the five lines showed 0-2% residualheterozygosity. Although this was a relatively small study, it can beseen using RFLPs that the lines had been highly homozygous prior to theseparate strain maintenance.

Inbred maize line PH20A is a yellow, dent maize inbred that is bestsuited as a female in crosses for producing first generation F₁ maizehybrids. Inbred maize line PH20A is best adapted to the Southeast andSouthcentral regions of the United States and can be used to producehybrids from approximately 115-120 relative maturity based on theComparative Relative Maturity Rating System for harvest moisture grain.Inbred maize line PH20A demonstrates above average Southern Leaf Blightand Southern Rust resistance. In hybrid combination and for its area ofadaptation, PH20A hybrids are high yielding and demonstrate good grainquality and above average Southern Rust Resistance.

The inbred has shown uniformity and stability within the limits ofenvironmental influence for all the traits as described in the VarietyDescription Information (Table 1) that follows. The Inbred has beenself-pollinated and ear-rowed a sufficient number of generations withcareful attention paid to uniformity of plant type to ensure thehomozygosity and phenotypic stability necessary to use in commercialproduction. The line has been increased both by hand and in isolatedfields with continued observation for uniformity. No variant traits havebeen observed or are expected in PH20A.

Inbred maize line PH20A, being substantially homozygous, can bereproduced by planting seeds of the line, growing the resulting maizeplants under self-pollinating or sib-pollinating conditions withadequate isolation, and harvesting the resulting seed, using techniquesfamiliar to the agricultural arts.

                  TABLE 1                                                         ______________________________________                                        VARIETY DESCRIPTION INFORMATION                                               INBRED = PH20A                                                                Type:                                                                              Dent                                                                     ______________________________________                                        A.   Maturity:                                                                     GDU Shed:         1520                                                        GDU Silk:         1560                                                        No. Reps:         4                                                      B.   Plant Characteristics:                                                        Plant height (to tassel tip):                                                                   265 cm                                                      Length of top ear internode:                                                                    16 cm                                                       Number of ears per stalk:                                                                       Single                                                      Ear height (to base of top ear):                                                                104 cm                                                      Number of tillers:                                                                              None                                                   C.   Leaf:                                                                         Color:            (B14) Dark Green*                                           Angle from Stalk: <30 degrees                                                 Marginal Waves:   (WF9) Few                                                   Number of Leaves (mature                                                                        22                                                          plants):                                                                      Sheath Pubescence:                                                                              (WF9) Medium                                                Longitudinal Creases:                                                                           (PA11) Many                                                 Length (Ear node leaf):                                                                         81 cm                                                       Width (widest point, ear node                                                                   10 cm                                                       leaf):                                                                   D.   Tassel:                                                                       Number lateral branches:                                                                        6                                                           Branch Angle from central                                                                       <30 degrees                                                 spike:                                                                        Pollen Shed:      Medium                                                      Peduncle Length (top leaf to                                                                    24 cm                                                       basal branches):                                                              Anther Color:     Yellow*                                                     Glume Color:      Green*                                                 E.   Ear (Husked Ear Data Except When Stated Otherwise):                           Length:           14 cm                                                       Weight:           123 mm                                                      Mid-point Diameter:                                                                             45 mm                                                       Silk Color:       Green*                                                      Husk Extension (Harvest stage):                                                                 Long (8-10 cm Beyond Ear Tip)                               Husk Leaf:        Long (>15 cm)                                               Taper of Ear:     Slight (Cylindrical)                                        Position of Shank (dry husks):                                                                  Upright                                                     Kernel Rows:      Straight, Distinct                                                            Number = 16                                                 Husk Color (fresh):                                                                             Light Green*                                                Husk Color (dry): Buff*                                                       Shank Length:     8 cm                                                        Shank (No. of internodes):                                                                      16                                                     F.   Kernel (Dried):                                                               Size (from ear mid-point)                                                     Length:           12 mm                                                       Width:            8 mm                                                        Thick:            5 mm                                                        Shape Grade (% rounds)                                                                          40-60                                                       Pericarp Color:   Colorless*                                                  Aleurone Color:   Homozygous Yellow*                                          Endosperm Color:  Yellow*                                                     Endosperm Type:   Normal Starch                                               Gm Wt/100 Seeds (unsized):                                                                      33 gm                                                  G    Cob:                                                                          Diameter at mid-point:                                                                          25 mm                                                       Strength:         Very Strong                                                 Color:            Red*                                                   H.   Diseases:                                                                     Corn Lethal Necrosis (MCMV =                                                                    Resistant                                                   Maize Chlorotic Mottle Virus                                                  and MDMV = Maize                                                              Dwarf Mosaic Virus):                                                          Maize Dwarf Mosaic Complex                                                                      Susceptible                                                 (MDMV & MCDV = Maize                                                          Dwarf Virus):                                                                 Anthracnose Stalk Rot (C.                                                                       Intermediate                                                graminicola):                                                                 S. Leaf Blight (B. maydis):                                                                     Resistant                                                   N. Leaf Blight (E. turcicum):                                                                   Resistant                                                   Common Rust (P. sorghi):                                                                        Susceptible                                                 Gray Leaf Spot (C. zeae):                                                                       Intermediate                                                Stewart's Wilt (E. stewartii):                                                                  Resistant                                                   Fusarium Ear Mold (F.                                                                           Intermediate                                                moniliforme):                                                            I.   Insects:                                                                      European Corn Borer-1 Leaf                                                                      Resistant                                                   Damage (Pre-flowering):                                                       European Corn Borer-2 (Post-                                                                    Resistant                                                   flowering):                                                              ______________________________________                                         The above descriptions are based on a scale of 1-9, 1 being highly            susceptible, 9 being highly resistant.                                        S (Susceptible): Would generally represent a score of 1-3.                    I (Intermediate): Would generally represent a score of 4-5.                   R (Resistant): Would generally represent a score of 6-7.                      H (Highly Resistant): Would generally represent a score of 8-9.               Highly resistant does not imply the inbred is immune.                         *In interpreting the foregoing color designations, reference may be had t     the Munsell Glossy Book of Color, a standard color reference.            

INDUSTRIAL APPLICABILITY

This invention also is directed to methods for producing a maize plantby crossing a first parent maize plant with a second parent maize plantwherein the first or second parent maize plant is an inbred maize plantof the line PH20A. Further, both first and second parent maize plantscan come from the inbred maize line PH20A. Thus, any such methods usingthe inbred maize line PH20A are part of this invention: selfing,backcrosses, hybrid production, crosses to populations, and the like.All plants produced using inbred maize line PH20A as a parent are withinthe scope of this invention. Advantageously, the inbred maize line isused in crosses with other, different, maize inbreds to produce firstgeneration (F₁) maize hybrid seeds and plants with superiorcharacteristics.

As used herein, the term plant includes plant cells, plant protoplasts,plant cell tissue cultures from which maize plants can be regenerated,plant calli, plant clumps, and plant cells that are intact in plants orparts of plants, such as embryos, pollen, ovules, flowers, kernels,ears, cobs, leaves, husks, stalks, roots, root tips, anthers, silk andthe like.

Duncan, Williams, Zehr, and Widholm, Planta (1985) 165:322-332 reflectsthat 97% of the plants cultured that produced callus were capable ofplant regeneration. Subsequent experiments with both inbreds and hybridsproduced 91% regenerable callus that produced plants. In a further studyin 1988, Songstad, Duncan & Widholm in Plant Cell Reports (1988),7:262-265 reports several media additions that enhance regenerability ofcallus of two inbred lines. Other published reports also indicated that"nontraditional" tissues are capable of producing somatic embryogenesisand plant regeneration. K. P. Rao, et al., Maize Genetics CooperationNewsletter, 60:64-65 (1986), refers to somatic embryogenesis from glumecallus cultures and B. V. Conger, et al., Plant Cell Reports, 6:345-347(1987) indicates somatic embryogenesis from the tissue cultures of maizeleaf segments. Thus, it is clear from the literature that the state ofthe art is such that these methods of obtaining plants are, and were,"conventional" in the sense that they are routinely used and have a veryhigh rate of success.

Tissue culture of maize is described in European Patent Application,publication 160,390, incorporated herein by reference. Maize tissueculture procedures are also described in Green and Rhodes, "PlantRegeneration in Tissue Culture of Maize," Maize for Biological Research(Plant Molecular Biology Association, Charlottesville, Va. 1982, at367-372) and in Duncan, et al., "The Production of Callus Capable ofPlant Regeneration from Immature Embryos of Numerous Zea MaysGenotypes," 165 Planta 322-332 (1985). Thus, another aspect of thisinvention is to provide cells which upon growth and differentiationproduce maize plants having the physiological morphologicalcharacteristics of inbred line PH20A.

Maize is used as human food, livestock feed, and as raw material inindustry. The food uses of maize, in addition to human consumption ofmaize kernels, include both products of dry- and wet-milling industries.The principal products of maize dry milling are grits, meal and flour.The maize wet-milling industry can provide maize starch, maize syrups,and dextrose for food use. Maize oil is recovered from maize germ, whichis a by-product of both dry- and wet-milling industries.

Maize, including both grain and non-grain portions of the plant, is alsoused extensively as livestock feed, primarily for beef cattle, dairycattle, hogs, and poultry.

Industrial uses of maize include production of ethanol, maize starch inthe wet-milling industry and maize flour in the dry-milling industry.The industrial applications of maize starch and flour are based onfunctional properties, such as viscosity, film formation, adhesiveproperties, and ability to suspend particles. The maize starch and flourhave application in the paper and textile industries. Other industrialuses include applications in adhesives, building materials, foundrybinders, laundry starches, explosives, oil-well muds, and other miningapplications.

Plant parts other than the grain of maize are also used in industry: forexample, stalks and husks are made into paper and wallboard and cobs areused for fuel and to make charcoal.

The seed of inbred maize line PH20A, the plant produced from the inbredseed, the hybrid maize plant produced from the crossing of the inbred,hybrid seed, and various parts of the hybrid maize plant can be utilizedfor human food, livestock feed, and as a raw material in industry.

Performance Examples of PH20A

In the examples that follow, the traits and characteristics of inbredmaize line PH20A are given as a line. The data collected on inbred maizeline PH20A is presented for the key characteristics and traits.

The results in Table 2A compare PH20A to PHMKO, a similarly adaptedline. The inbred per se results show that although inbred PHMKO issomewhat higher yielding, inbred PH20A exhibits a significantly highertest weight. Inbred PH20A demonstrates significantly higher seedlingvigor and early stand count. Although both inbreds exhibit good grainappearance, PH20A has a significantly better ear texture score thanPHMKO. Both inbreds have good resistance to Southern Leaf Blight.

The results in Table 2B compare PH20A to PHW52, a parent line of PH20A.The inbred per se results show that inbred PH20A has better seedlingvigor and stay green than inbred PHW52. Inbred PH20A demonstrates betterresistance to stalk lodging and better ear texture than PHW52. InbredPH20A also demonstrates better resistance to Southern Leaf Blight, GrayLeaf Spot, Northern Leaf Blight and First Generation European Corn Borerthan PHW52.

The results in Table 2C compare PH20A to PHKV1, a similarly adaptedline. The inbred per se results show that inbred PHKV1 is somewhathigher yielding than PH20A. Inbred PH20A has better seedling vigor thaninbred PHKVI. Although both inbred PHKV1 and inbred PH20A demonstrategood resistance to Southern Leaf Blight, PH20A demonstratessignificantly higher resistance to Gray Leaf Spot and Northern LeafBlight than PHKV1.

The results in Table 3A compare the Inbred By Tester performance ofPH20A and PHMKO, when crossed to the same inbred tester and grown in thesame experiment. The Inbred By Tester results show that in hybridcombination PH20A yields higher than PHMKO and has a higher test weight.The PH20A hybrids demonstrate significantly better seedling vigor andgrain appearance than the PHMKO hybrids. Both PH20A hybrids and PHMKOhybrids have good resistance to Southern Leaf Blight.

The results in Table 3B compare Inbred By Tester performance of PH20Ahybrids and PHW52 hybrids. The results show that in hybrid combinationPH20A hybrids are higher yielding than PHW52 hybrids and PH20A hybridsdemonstrate better seedling vigor than PHW52 hybrids. The PH20A hybridsalso exhibit significantly better stay green, grain appearance andresistance to Gray Leaf Spot than PHW52 hybrids.

The results in Table 3C compare Inbred By Tester performance of PH20Ahybrids and PHKV1 hybrids. The results show that PH20A hybrids aresignificantly higher yielding than PHKVI hybrids and PH20A hybrids havesignificantly superior grain appearance compared to PHKV1 hybrids.

The results in Table 4A compare a PH20A hybrid and a similarly adaptedPHW52 hybrid. The specific combining ability results show that the PH20Ahybrid is significantly higher yielding and demonstrates significantlybetter seedling vigor than the PHW52 hybrid. While both hybridsdemonstrate above average grain appearance, the PH20A hybriddemonstrates better resistance to Southern Leaf Blight, Southern Rust,Northern Leaf Blight, and Common Rust than the PHW52 hybrid.

The results in Table 4B compare a PH20A hybrid and a similarly adaptedPHHB9 hybrid. The specific combining ability results show that whileboth hybrids demonstrate above average yields, the PH20A hybriddemonstrates significantly better seedling vigor and grain appearancethan the PHHB9 hybrid. In addition, the PH20A hybrid exhibitssignificantly greater resistance to stalk lodging and brittle stalk thanthe PHHB9 hybrid. The PH20A hybrid also demonstrates better resistanceto Southern Leaf Blight, Southern Rust, and Northern Leaf Blight.

                                      TABLE 2A                                    __________________________________________________________________________    PAIRED INBRED COMPARISON REPORT                                               VARIETY #1 = PH20A                                                            VARIETY #2 = PHMK0                                                            __________________________________________________________________________               BU BU     TST                                                                              SDG EST                                                                              TIL                                                                              GDU                                                                              GDU                                                 ACR                                                                              ACR MST                                                                              WT VGR CNT                                                                              LER                                                                              SHD                                                                              SLK                                                 ABS                                                                              % MN                                                                              ABS                                                                              ABS                                                                              ABS ABS                                                                              ABS                                                                              ABS                                                                              ABS                                      __________________________________________________________________________    TOTAL SUM                                                                            1   63.6                                                                             98  23.1                                                                             55.5                                                                             5.6 32.1                                                                             3.7                                                                              153.8                                                                            157.8                                           2   64.7                                                                             104 21.9                                                                             53.9                                                                             4.3 29.3                                                                             1.9                                                                              157.3                                                                            164.1                                           LOCS                                                                              23 23  31 19 58  85 56 77 75                                              REPS                                                                              40 40  49 33 73  133                                                                              71 85 82                                              DIFF                                                                              1.1                                                                              5   1.2                                                                              1.7                                                                              1.2 2.8                                                                              1.7                                                                              3.5                                                                              6.3                                             PR > T                                                                            .801                                                                             .530                                                                              .019+                                                                            .000#                                                                            .000#                                                                             .008#                                                                            .406                                                                             .000#                                                                            .000#                                    __________________________________________________________________________               POL                                                                              TAS PLT                                                                              EAR                                                                              RT  STA                                                                              STK                                                                              BRT                                                                              GRN                                                 SC SZ  HT HT LDG GRN                                                                              LDG                                                                              STK                                                                              APP                                                 ABS                                                                              ABS ABS                                                                              ABS                                                                              ABS ABS                                                                              ABS                                                                              ABS                                                                              ABS                                      __________________________________________________________________________    TOTAL SUM                                                                            1   5.3                                                                              5.1 90.6                                                                             35.0                                                                             69.9                                                                              6.2                                                                              88.5                                                                             92.1                                                                             5.0                                             2   5.2                                                                              4.9 84.5                                                                             34.1                                                                             97.3                                                                              7.2                                                                              86.4                                                                             91.6                                                                             5.4                                             LOCS                                                                              20 35  43 43 10  34 14 13 12                                              REPS                                                                              21 37  57 57 16  43 27 18 20                                              DIFF                                                                              0.1                                                                              0.2 6.1                                                                              0.9                                                                              27.3                                                                              1.0                                                                              2.1                                                                              0.4                                                                              0.3                                             PR > T                                                                            .874                                                                             .283                                                                              .000#                                                                            .255                                                                             .045+                                                                             .007#                                                                            .630                                                                             .936                                                                             .470                                     __________________________________________________________________________               SCT                                                                              EAR TEX                                                                              EAR                                                                              BAR DRP                                                                              GLF                                                                              NLF                                                                              SLF                                                 GRN                                                                              SZ  EAR                                                                              MLD                                                                              PLT EAR                                                                              SPT                                                                              BLT                                                                              BLT                                                 ABS                                                                              ABS ABS                                                                              ABS                                                                              ABS ABS                                                                              ABS                                                                              ABS                                                                              ABS                                      __________________________________________________________________________    TOTAL SUM                                                                            1   5.6                                                                              5.1 7.2                                                                              6.3                                                                              92.5                                                                              100.0                                                                            3.7                                                                              5.7                                                                              7.0                                             2   5.7                                                                              5.4 4.6                                                                              6.2                                                                              90.0                                                                              98.3                                                                             7.2                                                                              6.8                                                                              7.5                                             LOCS                                                                              27 17  14 23 43  4  21 10 10                                              REPS                                                                              29 17  14 26 51  8  33 18 18                                              DIFF                                                                              0.1                                                                              0.4 2.6                                                                              0.1                                                                              2.5 1.7                                                                              3.5                                                                              1.1                                                                              0.5                                             PR > T                                                                            .711                                                                             .303                                                                              .000#                                                                            .787                                                                             .322                                                                              .100                                                                             .000#                                                                            .024+                                                                            .054*                                    __________________________________________________________________________               STW                                                                              ANT HD    MDM FUS                                                                              ECB                                                                              ECB                                                                              ECB                                                 WLT                                                                              ROT SMT                                                                              CLN                                                                              CPX ERS                                                                              DPE                                                                              1LF                                                                              2SC                                                 ABS                                                                              ABS ABS                                                                              ABS                                                                              ABS ABS                                                                              ABS                                                                              ABS                                                                              ABS                                      __________________________________________________________________________    TOTAL SUM                                                                            1   5.2                                                                              4.4 100.0                                                                            5.5                                                                              2.9 5.2                                                                              100.0                                                                            6.4                                                                              5.0                                             2   7.3                                                                              4.9 100.0                                                                            4.5                                                                              2.6 5.4                                                                              100.0                                                                            5.5                                                                              7.5                                             LOCS                                                                              6  7   1  1  6   19 1  4  1                                               REPS                                                                              8  11  2  2  10  26 2  5  2                                               DIFF                                                                              2.2                                                                              0.4 0.0                                                                              1.0                                                                              0.3 0.2                                                                              0.0                                                                              0.9                                                                              2.5                                             PR > T                                                                            .021+                                                                            .395      .175                                                                              .581  .391                                        __________________________________________________________________________     * = 10% SIG                                                                   + = 5% SIG                                                                    # = 1% SIG                                                               

                                      TABLE 2B                                    __________________________________________________________________________    PAIRED INBRED COMPARISON REPORT                                               VARIETY #1 = PH20A                                                            VARIETY #2 = PHW52                                                            __________________________________________________________________________               BU BU     TST                                                                              SDG                                                                              EST                                                                              TIL GDU                                                                              GDU                                                 ACR                                                                              ACR MST                                                                              WT VGR                                                                              CNT                                                                              LER SHD                                                                              SLK                                                 ABS                                                                              % MN                                                                              ABS                                                                              ABS                                                                              ABS                                                                              ABS                                                                              ABS ABS                                                                              ABS                                      __________________________________________________________________________    TOTAL SUM                                                                            1   66.2                                                                             99  24.6                                                                             55.3                                                                             5.5                                                                              35.1                                                                             3.4 153.0                                                                            157.2                                           2   69.3                                                                             103 19.2                                                                             57.6                                                                             4.8                                                                              34.0                                                                             1.4 148.1                                                                            153.1                                           LOCS                                                                              37 37  49 31 65 102                                                                              64  83 81                                              REPS                                                                              67 67  82 56 88 159                                                                              82  90 87                                              DIFF                                                                              3.0                                                                              5   5.3                                                                              2.3                                                                              0.7                                                                              1.1                                                                              2.0 4.9                                                                              4.1                                             PR > T                                                                            .342                                                                             .304                                                                              .000#                                                                            .000#                                                                            .000#                                                                            .156                                                                             .271                                                                              .000#                                                                            .000#                                    __________________________________________________________________________               POL                                                                              POL POL                                                                              TAS                                                                              PLT                                                                              EAR                                                                              RT  STA                                                                              STK                                                 WT WT  SC SZ HT HT LDG GRN                                                                              LDG                                                 ABS                                                                              % MN                                                                              ABS                                                                              ABS                                                                              ABS                                                                              ABS                                                                              ABS ABS                                                                              ABS                                      __________________________________________________________________________    TOTAL SUM                                                                            1   127.0                                                                            71  5.3                                                                              5.0                                                                              92.6                                                                             36.1                                                                             76.4                                                                              6.2                                                                              91.7                                            2   219.0                                                                            131 5.4                                                                              5.7                                                                              76.1                                                                             26.2                                                                             97.8                                                                              5.1                                                                              80.7                                            LOCS                                                                              5  5   22 37 54 53 13  41 20                                              REPS                                                                              5  5   22 39 75 73 22  59 38                                              DIFF                                                                              92.0                                                                             60  0.1                                                                              0.7                                                                              16.5                                                                             9.9                                                                              21.3                                                                              1.1                                                                              11.0                                            PR > T                                                                            .065*                                                                            .109                                                                              .746                                                                             .006#                                                                            .000#                                                                            .000#                                                                            .026+                                                                             .000#                                                                            .003#                                    __________________________________________________________________________               BRT                                                                              GRN SCT                                                                              EAR                                                                              TEX                                                                              EAR                                                                              BAR DRP                                                                              GLF                                                 STK                                                                              APP GRN                                                                              SZ EAR                                                                              MLD                                                                              PLT EAR                                                                              SPT                                                 ABS                                                                              ABS ABS                                                                              ABS                                                                              ABS                                                                              ABS                                                                              ABS ABS                                                                              ABS                                      __________________________________________________________________________    TOTAL SUM                                                                            1   85.3                                                                             5.0 5.6                                                                              5.1                                                                              7.2                                                                              6.3                                                                              92.3                                                                              100.0                                                                            3.6                                             2   90.4                                                                             6.3 6.1                                                                              6.0                                                                              6.0                                                                              5.4                                                                              94.2                                                                              99.5                                                                             2.4                                             LOCS                                                                              17 16  28 16 15 24 49  4  15                                              REPS                                                                              23 28  30 16 15 27 59  8  23                                              DIFF                                                                              5.1                                                                              1.3 0.4                                                                              0.9                                                                              1.2                                                                              0.9                                                                              1.9 0.5                                                                              1.2                                             PR > T                                                                            .222                                                                             .014+                                                                             .206                                                                             .034+                                                                            .001#                                                                            .003#                                                                            .243                                                                              .391                                                                             .001#                                    __________________________________________________________________________               NLF                                                                              SLF STW                                                                              ANT                                                                              HD    MDM FUS                                                                              COM                                                 BLT                                                                              BLT WLT                                                                              ROT                                                                              SMT                                                                              CLN                                                                              CPX ERS                                                                              RST                                                 ABS                                                                              ABS ABS                                                                              ABS                                                                              ABS                                                                              ABS                                                                              ABS ABS                                                                              ABS                                      __________________________________________________________________________    TOTAL SUM                                                                            1   5.8                                                                              6.6 5.2                                                                              3.9                                                                              100.0                                                                            5.5                                                                              3.0 5.3                                                                              4.0                                             2   4.1                                                                              5.8 4.3                                                                              3.2                                                                              100.0                                                                            5.5                                                                              2.8 4.6                                                                              4.0                                             LOCS                                                                              6  6   6  5  1  1  2   14 2                                               REPS                                                                              10 11  8  9  2  2  4   17 2                                               DIFF                                                                              1.7                                                                              0.8 0.9                                                                              0.7                                                                              0.0                                                                              0.0                                                                              0.3 0.7                                                                              0.0                                             PR > T                                                                            .001#                                                                            .042+                                                                             .159                                                                             .184     .500                                                                              .158                                                                             .999                                     __________________________________________________________________________               ECB                                                                           1LF                                                                           ABS                                                                __________________________________________________________________________    TOTAL SUM                                                                            1   7.0                                                                       2   2.7                                                                       LOCS                                                                              3                                                                         REPS                                                                              3                                                                         DIFF                                                                              4.3                                                                       PR > T                                                                            .006#                                                              __________________________________________________________________________     * = 10% SIG                                                                   + = 5% SIG                                                                    # = 1% SIG                                                               

                                      TABLE 2C                                    __________________________________________________________________________    PAIRED INBRED COMPARISON REPORT                                               VARIETY #1 = PH20A                                                            VARIETY #2 = PHKV1                                                            __________________________________________________________________________               BU BU     TST SDG                                                                              EST                                                                              TIL                                                                              GDU                                                                              GDU                                                 ACR                                                                              ACR MST                                                                              WT  VGR                                                                              CNT                                                                              LER                                                                              SHD                                                                              SLK                                                 ABS                                                                              % MN                                                                              ABS                                                                              ABS ABS                                                                              ABS                                                                              ABS                                                                              ABS                                                                              ABS                                      __________________________________________________________________________    TOTAL SUM                                                                            1   61.1                                                                             88  24.2                                                                             55.0                                                                              5.7                                                                              29.6                                                                             4.0                                                                              153.0                                                                            157.2                                           2   64.5                                                                             100 22.4                                                                             56.5                                                                              4.3                                                                              27.6                                                                             1.7                                                                              159.9                                                                            161.0                                           LOCS                                                                              20 20  27 16  56 80 55 72 70                                              REPS                                                                              34 34  41 26  66 121                                                                              66 74 72                                              DIFF                                                                              3.4                                                                              12  1.8                                                                              1.6 1.4                                                                              2.0                                                                              2.3                                                                              6.9                                                                              3.8                                             PR > T                                                                            .454                                                                             .192                                                                              .000#                                                                            .003#                                                                             .000#                                                                            .025+                                                                            .291                                                                             .000#                                                                            .000#                                    __________________________________________________________________________               POL                                                                              TAS PLT                                                                              EAR RT STA                                                                              STA                                                                              BRT                                                                              GRN                                                 SC SZ  HT HT  LDG                                                                              GRN                                                                              LDG                                                                              STK                                                                              APP                                                 ABS                                                                              ABS ABS                                                                              ABS ABS                                                                              ABS                                                                              ABS                                                                              ABS                                                                              ABS                                      __________________________________________________________________________    TOTAL SUM                                                                            1   5.4                                                                              5.0 89.8                                                                             35.0                                                                              69.9                                                                             6.0                                                                              86.3                                                                             89.5                                                                             5.4                                             2   3.2                                                                              3.1 81.3                                                                             32.8                                                                              91.0                                                                             5.6                                                                              88.8                                                                             96.6                                                                             7.9                                             LOCS                                                                              18 37  43 43  10 29 10 13 7                                               REPS                                                                              18 39  54 54  16 35 18 16 10                                              DIFF                                                                              2.3                                                                              1.9 8.6                                                                              2.2 21.1                                                                             0.5                                                                              2.5                                                                              7.0                                                                              2.6                                             PR > T                                                                            .000#                                                                            .000#                                                                             .000#                                                                            .026+                                                                             .058*                                                                            .058*                                                                            .151                                                                             .159                                                                             .012+                                    __________________________________________________________________________               SCT                                                                              EAR TEX                                                                              EAR BAR                                                                              GLF                                                                              NLF                                                                              SLF                                                                              STW                                                 GRN                                                                              SZ  EAR                                                                              MLD PLT                                                                              SPT                                                                              BLT                                                                              BLT                                                                              WLT                                                 ABS                                                                              ABS ABS                                                                              ABS ABS                                                                              ABS                                                                              ABS                                                                              ABS                                                                              ABS                                      __________________________________________________________________________    TOTAL SUM                                                                            1   5.6                                                                              5.1 7.1                                                                              6.3 92.3                                                                             3.9                                                                              5.6                                                                              7.0                                                                              5.2                                             2   6.7                                                                              5.1 7.0                                                                              6.8 92.8                                                                             3.0                                                                              3.5                                                                              6.3                                                                              6.2                                             LOCS                                                                              29 17  15 25  36 23 11 10 6                                               REPS                                                                              31 17  15 28  41 35 19 18 8                                               DIFF                                                                              1.0                                                                              0.0 0.1                                                                              0.5 0.5                                                                              0.9                                                                              2.1                                                                              0.7                                                                              1.0                                             PR > T                                                                            .000#                                                                            .999                                                                              .670                                                                             .136                                                                              .747                                                                             .002#                                                                            .000#                                                                            .039+                                                                            .067*                                    __________________________________________________________________________               ANT                                                                              HD     MDM FUS                                                                              COM                                                                              ECB                                                                              ECB                                                                              ECB                                                 ROT                                                                              SMT CLN                                                                              CPX ERS                                                                              RST                                                                              DPE                                                                              1LF                                                                              2SC                                                 ABS                                                                              ABS ABS                                                                              ABS ABS                                                                              ABS                                                                              ABS                                                                              ABS                                                                              ABS                                      __________________________________________________________________________    TOTAL SUM                                                                            1   4.1                                                                              100.0                                                                             5.5                                                                              2.9 5.2                                                                              3.5                                                                              100.0                                                                            6.2                                                                              5.0                                             2   4.3                                                                              100.0                                                                             6.0                                                                              3.5 6.4                                                                              1.8                                                                              87.5                                                                             3.7                                                                              3.5                                             LOCS                                                                              7  1   1  6   19 3  1  3  1                                               REPS                                                                              13 2   2  11  25 4  2  4  2                                               DIFF                                                                              0.2                                                                              0.0 0.5                                                                              0.6 1.2                                                                              1.7                                                                              12.5                                                                             2.5                                                                              1.5                                             PR > T                                                                            .573      .013+                                                                             .004#                                                                            .199  .013+                                       __________________________________________________________________________     * = 10% SIG                                                                   + = 5% SIG                                                                    # = 1% SIG                                                               

                                      TABLE 3A                                    __________________________________________________________________________    Average Inbred By Tester Performance Comparing PH20A To PHMK0 Crossed         To The Same Inbred Testers And Grown In The Same Experiments.                 __________________________________________________________________________               SEL     BU  BU  PRM     TST SDG EST GDU                                       IND PRM ACR ACR SHD MST WT  VGR CNT SHD                                       % MN                                                                              ABS ABS % MN                                                                              ABS % MN                                                                              ABS % MN                                                                              % MN                                                                              % MN                           __________________________________________________________________________    TOTAL SUM                                                                            REPS                                                                              25  28  142 142 14  164 85  52  41  22                                    LOCS                                                                              25  28  131 131 14  145 80  40  34  21                                    PH20A                                                                             99  119 175 107 114 106 58  99  95  100                                   PHMK0                                                                             102 116 170 105 115 102 57  88  104 102                                   DIFF                                                                              4   3   5   2   1   4   1   11  9   2                                     PR > T                                                                            0.13                                                                              0.00                                                                              0.07                                                                              0.14                                                                              0.18                                                                              0.00                                                                              0.00                                                                              0.02                                                                              0.01                                                                              0.01                           __________________________________________________________________________               GDU STK PLT EAR RT  STA STK BRT GRN SLF                                       SLK CNT HT  HT  LDG GRN LDG STK APP BLT                                       % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              ABS                            __________________________________________________________________________    TOTAL SUM                                                                            REPS                                                                              16  176 80  80  48  105 92  5   18  4                                     LOCS                                                                              16  153 71  71  39  88  80  3   18  4                                     PH20A                                                                             100 98  105 107 88  90  96  102 113 7                                     PHMK0                                                                             102 99  103 103 96  99  101 103 91  6                                     DIFF                                                                              2   1   2   4   8   9   5   1   22  1                                     PR > T                                                                            0.01                                                                              0.17                                                                              0.01                                                                              0.00                                                                              0.18                                                                              0.02                                                                              0.01                                                                              0.62                                                                              0.00                                                                              0.39                           __________________________________________________________________________               FUS ECB DRP GLF                                                               ERS 2SC EAR SPT                                                               ABS ABS % MN                                                                              ABS                                                    __________________________________________________________________________    TOTAL SUM                                                                            REPS                                                                              6   5   2   8                                                             LOCS                                                                              6   3   1   8                                                             PH20A                                                                             7   4   100 4                                                             PHMK0                                                                             7   3   101 6                                                             DIFF                                                                              0   1   1   1                                                             PR > T                                                                            1.00                                                                              0.63    0.03                                                   __________________________________________________________________________     *PR > T values are valid only for comparisons with Locs >= 10.           

                                      TABLE 3B                                    __________________________________________________________________________    Average Inbred By Tester Performance Comparing PH20A To PHW52 Crossed         To The Same Inbred Testers And Grown In The Same Experiments.                 __________________________________________________________________________               SEL     BU  BU  PRM     TST SDG EST GDU                                       IND PRM ACR ACR SHD MST WT  VGR CNT SHD                                       % MN                                                                              ABS ABS % MN                                                                              ABS % MN                                                                              ABS % MN                                                                              % MN                                                                              % MN                           __________________________________________________________________________    TOTAL SUM                                                                            REPS                                                                              13  15  117 117 7   139 78  54  54  22                                    LOCS                                                                              13  15  100 100 7   113 68  40  44  20                                    PH20A                                                                             101 119 182 108 115 107 58  102 99  102                                   PHW52                                                                             99  115 168 100 114 100 58  96  102 101                                   DIFF                                                                              2   4   15  8   1   7   0   5   3   1                                     PR > T                                                                            0.73                                                                              0.00                                                                              0.00                                                                              0.00                                                                              0.06                                                                              0.00                                                                              0.40                                                                              0.15                                                                              0.16                                                                              0.10                           __________________________________________________________________________               GDU STK PLT EAR RT  STA STK BRT GRN SLF                                       SLK CNT HT  HT  LDG GRN LDG STK APP BLT                                       % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              ABS                            __________________________________________________________________________    TOTAL SUM                                                                            REPS                                                                              13  151 64  64  56  88  95  15  32  4                                     LOCS                                                                              13  120 52  52  44  67  78  12  28  2                                     PH20A                                                                             103 99  105 110 87  105 98  102 111 5                                     PHW52                                                                             102 101 99  95  106 91  99  100 105 4                                     DIFF                                                                              1   2   6   15  19  14  1   2   6   2                                     PR > T                                                                            0.05                                                                              0.02                                                                              0.00                                                                              0.00                                                                              0.00                                                                              0.00                                                                              0.45                                                                              0.33                                                                              0.04                                                                              0.26                           __________________________________________________________________________               FUS ECB DRP GLF                                                               ERS 2SC EAR SPT                                                               ABS ABS % MN                                                                              ABS                                                    __________________________________________________________________________    TOTAL SUM                                                                            REPS                                                                              2   5   22  4                                                             LOCS                                                                              2   3   16  4                                                             PH20A                                                                             8   4   100 6                                                             PHW52                                                                             6   6   100 4                                                             DIFF                                                                              1   2   1   2                                                             PR > T                                                                            0.13                                                                              0.04                                                                              0.03                                                                              0.02                                                   __________________________________________________________________________     *PR > T values are valid only for comparisons with Locs >= 10.           

                                      TABLE 3C                                    __________________________________________________________________________    Average Inbred By Tester Performance Comparing PH20A To PHKV1 Crossed         To The Same Inbred Testers And Grown In The Same Experiments                  __________________________________________________________________________               SEL     BU  BU  PRM     TST SDG EST GDU                                       IND PRM ACR ACR SHD MST WT  VGR CNT SHD                                       % MN                                                                              ABS ABS % MN                                                                              ABS % MN                                                                              ABS % MN                                                                              % MN                                                                              % MN                           __________________________________________________________________________    TOTAL SUM                                                                            REPS                                                                              18  29  137 137 9   143 93  32  48  16                                    LOCS                                                                              18  29  136 136 9   141 91  32  48  16                                    PH20A                                                                             106 119 180 108 114 108 57  102 95  101                                   PHKV1                                                                             99  118 166 99  116 105 57  100 103 104                                   DIFF                                                                              6   2   14  9   2   3   0   2   8   3                                     PR > T                                                                            0.07                                                                              0.00                                                                              0.00                                                                              0.00                                                                              0.04                                                                              0.01                                                                              0.77                                                                              0.50                                                                              0.00                                                                              0.00                           __________________________________________________________________________               GDU STK PLT EAR RT  STA STK BRT GRN ECB                                       SLK CNT HT  HT  LDG GRN LDG STK APP 2SC                                       % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              ABS                            __________________________________________________________________________    TOTAL SUM                                                                            REPS                                                                              8   156 64  64  43  53  83  5   31  2                                     LOCS                                                                              8   152 64  64  40  53  80  5   31  2                                     PH20A                                                                             101 99  105 108 85  103 100 97  113 7                                     PHKV1                                                                             104 100 104 110 98  101 97  98  100 1                                     DIFF                                                                              3   1   1   2   13  2   3   0   13  6                                     PR > T                                                                            0.04                                                                              0.11                                                                              0.18                                                                              0.13                                                                              0.10                                                                              0.78                                                                              0.07                                                                              0.88                                                                              0.00                               __________________________________________________________________________               DRP GLF                                                                       EAR SPT                                                                       % MN                                                                              ABS                                                            __________________________________________________________________________    TOTAL SUM                                                                            REPS                                                                              2   9                                                                     LOCS                                                                              2   9                                                                     PH20A                                                                             100 5                                                                     PHKV1                                                                             100 4                                                                     DIFF                                                                              0   1                                                                     PR > T  0.25                                                           __________________________________________________________________________     *PR > T values are valid only for comparisons with Locs >= 10.           

                                      TABLE 4A                                    __________________________________________________________________________    VARIETY #1 = PH20A/PH67A                                                      VARIETY #2 = PHW52/PHR03                                                      __________________________________________________________________________                   PRM BU  BU      TST SDG EST GDU                                           PRM SHD ACR ACR MST WT  VGR CNT SHD                                           ABS ABS ABS % MN                                                                              % MN                                                                              ABS % MN                                                                              % MN                                                                              % MN                               __________________________________________________________________________    TOTAL SUM                                                                            1   115 113 170.3                                                                             105 105 57.4                                                                              110 99  101                                       2   114 114 163.8                                                                             102 102 58.2                                                                              101 102 102                                       LOCS                                                                              51  50  229 229 239 128 108 107 62                                        REPS                                                                              51  50  300 300 312 161 149 141 74                                        DIFF                                                                              1   1   6.5 4   3   0.8 9   3   1                                         PR > T                                                                            .000#                                                                             .000#                                                                             .000#                                                                             .000#                                                                             .000#                                                                             .000#                                                                             .000#                                                                             .001#                                                                             .001#                              __________________________________________________________________________               GDU STK PLT EAR RT  STA STK BRT GRN                                           SLK CNT HT  HT  LDG GRN LDG STK APP                                           % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                               __________________________________________________________________________    TOTAL SUM                                                                            1   102 100 105 102 96  86  101 103 106                                       2   103 101 99  96  105 101 101 105 106                                       LOCS                                                                              39  283 113 116 87  101 167 20  35                                        REPS                                                                              42  389 138 140 118 136 209 27  38                                        DIFF                                                                              1   1   5   6   9   15  0   2   1                                         PR > T                                                                            .195                                                                              .180                                                                              .000#                                                                             .000#                                                                             .013+                                                                             .001#                                                                             .999                                                                              .141                                                                              .803                               __________________________________________________________________________               DRP GLF NLF SLF GOS STW ANT HD                                                EAR SPT BLT BLT WLT WLT ROT SMT CLN                                           % MN                                                                              ABS ABS ABS ABS ABS ABS ABS ABS                                __________________________________________________________________________    TOTAL SUM                                                                            1   100 4.1 5.7 6.9 7.8 7.0 3.4 97.2                                                                              5.8                                       2   101 4.3 2.8 4.5 8.0 4.5 2.9 94.4                                                                              4.8                                       LOCS                                                                              44  25  7   6   2   2   8   3   2                                         REPS                                                                              54  35  15  11  4   2   17  6   4                                         DIFF                                                                              0   0.2 2.8 2.4 0.3 2.5 0.5 2.8 1.0                                       PR > T                                                                            .999                                                                              .265                                                                              .001#                                                                             .002#                                                                             .500                                                                              .126                                                                              .060*                                                                             .481                                                                              .295                               __________________________________________________________________________               MDM FUS GIB COM SOU ECB ECB ECB ECB                                           CPX ERS ERS RST RST DPE 1LF 2SC 2IT                                           ABS ABS ABS ABS ABS ABS ABS ABS ABS                                __________________________________________________________________________    TOTAL SUM                                                                            1   3.0 6.4 8.5 5.0 5.0 100.0                                                                             4.3 4.5 2.7                                       2   2.6 5.7 7.0 4.0 2.5 98.1                                                                              3.5 4.8 1.8                                       LOCS                                                                              4   7   1   2   2   2   4   12  1                                         REPS                                                                              10  11  2   3   4   4   9   18  3                                         DIFF                                                                              0.4 0.6 1.5 1.0 2.5 1.9 0.8 0.3 0.9                                       PR > T                                                                            .229                                                                              .391    .000#                                                                             .000#                                                                             .500                                                                              .182                                                                              .677                                   __________________________________________________________________________     * = 10% SIG                                                                   + = 5% SIG                                                                    # = 1% SIG                                                               

                                      TABLE 4B                                    __________________________________________________________________________    VARIETY #1 = PH20A/PH67A                                                      VARIETY #2 = PHHB9/PHBE2                                                      __________________________________________________________________________                   PRM BU  BU      TST SDG EST GDU                                           PRM SHD ACR ACR MST WT  VGR CNT SHD                                           ABS ABS ABS % MN                                                                              % MN                                                                              ABS % MN                                                                              % MN                                                                              % MN                               __________________________________________________________________________    TOTAL SUM                                                                            1   115 113 173.9                                                                             108 106 57.7                                                                              112 99  101                                       2   113 113 174.5                                                                             109 100 57.3                                                                              97  102 101                                       LOCS                                                                              67  52  305 305 313 162 107 111 63                                        REPS                                                                              67  52  361 361 371 189 137 138 74                                        DIFF                                                                              2   0   0.6 1   6   0.4 15  3   0                                         PR > T                                                                            .000#                                                                             .999                                                                              .622                                                                              .213                                                                              .000#                                                                             .001#                                                                             .000#                                                                             .006#                                                                             .999                               __________________________________________________________________________               GDU STK PLT EAR RT  STA STK BRT GRN                                           SLK CNT HT  HT  LDG GRN LDG STK APP                                           % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                                                                              % MN                               __________________________________________________________________________    TOTAL SUM                                                                            1   103 100 105 102 96  89  101 103 104                                       2   101 102 101 97  119 107 97  96  94                                        LOCS                                                                              45  362 131 134 99  100 209 20  41                                        REPS                                                                              47  455 152 154 127 124 241 27  41                                        DIFF                                                                              2   1   4   5   23  18  3   7   10                                        PR > T                                                                            .000#                                                                             .007#                                                                             .000#                                                                             .000#                                                                             .001#                                                                             .000#                                                                             .003#                                                                             .011+                                                                             .016+                              __________________________________________________________________________               DRP GLF NLF SLF GOS STW ANT HD                                                EAR SPT BLT BLT WLT WLT ROT SMT CLN                                           % MN                                                                              ABS ABS ABS ABS ABS ABS ABS ABS                                __________________________________________________________________________    TOTAL SUM                                                                            1   100 4.3 5.7 6.9 7.8 7.0 3.4 97.2                                                                              5.8                                       2   100 4.9 4.0 4.9 8.0 7.0 3.5 99.2                                                                              4.8                                       LOCS                                                                              92  24  7   5   2   2   8   3   2                                         REPS                                                                              97  34  15  10  4   2   17  6   4                                         DIFF                                                                              0   0.6 1.7 2.0 0.3 0.0 0.1 2.0 1.0                                       PR > T                                                                            .999                                                                              .062*                                                                             .002#                                                                             .058*                                                                             .500                                                                              .999                                                                              .932                                                                              .184                                                                              .295                               __________________________________________________________________________               MDM FUS GIB COM SOU ECB ECB ECB ECB                                           CPX ERS ERS RST RST DPE 1LF 2SC 2IT                                           ABS ABS ABS ABS ABS ABS ABS ABS ABS                                __________________________________________________________________________    TOTAL SUM                                                                            1   3.0 6.3 8.5 5.0 5.3 100.0                                                                             4.3 4.5 2.7                                       2   4.1 4.7 8.0 5.5 4.3 100.0                                                                             3.9 4.5 1.5                                       LOCS                                                                              4   5   1   1   3   3   4   12  1                                         REPS                                                                              10  9   2   2   5   5   9   18  3                                         DIFF                                                                              1.1 1.6 0.5 0.5 1.0 0.0 0.4 0.0 1.1                                       PR > T                                                                            .001#                                                                             .061*       .000#                                                                             .999                                                                              .391                                                                              .999                                   __________________________________________________________________________     * = 10% SIG                                                                   + = 5% SIG                                                                    # = 1% SIG                                                               

Deposits

Applicants have made a deposit of at least 2500 seeds of Inbred CornLine PH20A with the American Type Culture Collection (ATCC), Rockville,Md. 20852 U.S.A., ATCC Deposit No. 209521. The seeds deposited with theATCC on Dec. 8, 1997 were taken from the deposit maintained by PioneerHi-Bred International, Inc., 700 Capital Square, 400 Locust Street, DesMoines, Iowa 50309-2340 since prior to the filing date of thisapplication. This deposit of the Inbred Corn Line PH20A will bemaintained in the ATCC depository, which is a public depository, for aperiod of 30 years, or 5 years after the most recent request, or for theeffective life of the patent, whichever is longer, and will be replacedif it becomes nonviable during that period. Additionally, Applicantshave satisfied all the requirements of 37 C.F.R. §§1.801-1.809,including providing an indication of the viability of the sample.Applicants impose no restrictions on the availability of the depositedmaterial from the ATCC; however, Applicants have no authority to waiveany restrictions imposed by law on the transfer of biological materialor its transportation in commerce. Applicants do not waive anyinfringement of their rights granted under this patent or under thePlant Variety Protection Act (7 USC 2321 et seq.). U.S. Plant VarietyProtection of PH20A has been applied for under Application No. 9600166.

The foregoing invention has been described in detail by way ofillustration and example for purposes of clarity and understanding.However, it will be obvious that certain changes and modifications suchas single gene modifications and mutations, somoclonal variants, variantindividuals selected from large populations of the plants of the instantinbred and the like may be practiced within the scope of the invention,as limited only by the scope of the appended claims.

What is claimed is:
 1. Seed of maize inbred line designated PH20A havingbeen deposited under ATCC Accession No.
 209521. 2. A maize plant, orparts thereof, of inbred line PH20A, seed of said line having beendeposited under ATCC accession No.
 209521. 3. Pollen of the plant ofclaim
 2. 4. An ovule of the plant of claim
 2. 5. A maize plant, or partsthereof, having all the physiological and morphological characteristicsof the plant of claim
 2. 6. A male sterile maize plant, or partsthereof, otherwise having all the physiological and morphologicalcharacteristics of the plant of claim
 2. 7. A tissue culture ofregenerable cells of a maize plant of inbred line PH20A, seed of saidinbred line having been deposited under ATCC Accession No. 209521,wherein the tissue regenerates plants capable of expressing all themorphological and physiological characteristics of plants of said inbredline PH20A.
 8. A tissue culture according to claim 7, the cells orprotoplasts being of a tissue selected from the group consisting ofleaves, pollen, embryos, roots, root tips, anthers, silks, flowers,kernels, ears, cobs, husks, and stalks.
 9. A maize plant regeneratedfrom the tissue culture of claim 7, capable of expressing all themorphological and physiological characteristics of inbred line PH20A,seed of said inbred line having been deposited under ATCC Accession No.209521.
 10. A method for producing a first generation (F₁) hybrid maizeseed comprising crossing the plant of claim 2 with a different inbredparent maize plant and harvesting the resultant first generation (F₁)hybrid maize seed.
 11. The method of claim 10 wherein inbred maize plantof claim 2 is the female parent.
 12. The method of claim 10 whereininbred maize plant of claim 2 is the male parent.
 13. A method forproducing a first generation (F₁) hybrid maize seed comprising crossingthe plant of claim 5 with a different inbred parent maize plant andharvesting the resultant first generation (F₁) hybrid maize seed. 14.The method of claim 13 wherein inbred maize plant of claim 5 is thefemale parent.
 15. The method of claim 13 wherein inbred maize plant ofclaim 5 is the male parent.
 16. An F₁ hybrid seed produced by crossingthe inbred maize plant according to claim 2 with another, differentmaize plant.
 17. An F₁ hybrid plant, or parts thereof, grown from theseed of claim
 16. 18. An F₁ hybrid seed produced by crossing the inbredmaize plant according to claim 5 with another, different maize plant.19. An F₁ hybrid plant, or parts thereof, grown from the seed of claim18.